JPH05339622A - Heating method for vacuum degassing chamber - Google Patents

Abstract

PURPOSE:To provide the method for heating the inside of a vacuum degassing chamber by using high-temp. combustion flames. CONSTITUTION:This method for heating the vacuum degassing chamber consists in inserting a burner 1 for heating into the vacuum degassing chamber 4 from the top part of the vacuum degassing chamber 4 in the state of opening only the immersion pipe part of the vacuum degassing chamber 4 and controlling the quantity of the air for secondary combustion to be supplied to the center of the annular high-temp. combustion flames of the burner 1, thereby controlling the radiation energy quantity from the high-temp. combustion flame. Further, the insertion position of the burner 1 for heating is properly controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for heating the inside of a vacuum degassing tank with a high temperature combustion flame.

[0002]

2. Description of the Related Art Gaseous impurities are removed or carbon in steel is carbonized by subjecting molten steel to vacuum degassing.
It is known to be released as O gas to produce ultra low carbon steel. Examples of this vacuum degassing treatment method include so-called RH vacuum degassing treatment in which molten steel in a ladle is refined in a process of circulating it in a vacuum degassing tank, or sucking up molten steel,
A so-called D-H type vacuum degassing process is used in which refining is performed in the discharging process.

In order to minimize a decrease in molten steel temperature during the vacuum degassing process, it is practiced to preheat the vacuum degassing tank in advance. Further, in the process of the vacuum degassing process, when bubbles in the molten steel separate from the molten steel interface, a splash is generated, and if the molten steel particles or the molten metal floats on the molten steel surface, the molten metal droplets fly. To do. These droplets adhere to the inner wall of the vacuum degassing tank and vary depending on the height of the vacuum degassing tank.
It deposits significantly in the range of 0 mm.

Various methods of heating have been proposed for preheating in the vacuum degassing tank or for dissolving and removing metal or the like. As a method of using a burner combustion flame, for example, Japanese Patent Publication No. 45-31062. As proposed, a burner is arranged at the lower end of the dip tube provided at the bottom of the vacuum degassing tank, an exhaust port is provided at the top of the vacuum degassing tank, and a combustion flame is made to flow upward from the bottom. A method of preheating the vacuum degassing tank. Further, as proposed in Japanese Patent Laid-Open No. 01-159312, a burner is inserted at the top of the vacuum degassing tank to generate a combustion flame, and the combustion gas is provided with an exhaust flue provided on the upper side surface of the vacuum degassing tank. And a method of performing preheating in the vacuum degassing tank and dissolving and removing the adhered metal by distributing it to both of the immersion pipes provided in the lower part and the lower part and discharging it to the outside.

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the case of the No. 062 preheating method, since a combustion flame is generated in the immersion pipe portion having a relatively small inner diameter, if a high temperature combustion flame is used, only the immersion pipe portion locally becomes high in temperature, which causes excessive preheating. Inherent. In addition, it is difficult to prevent air from entering through the gap between the dip tube and the burner, and because the intervening air is present between the combustion flame and the inner wall, the heating efficiency is poor, etc. The temperature inside the vacuum degassing tank is only about 800-1000 ° C. I can't preheat.

The heating method of the above-mentioned Japanese Patent Laid-Open No. 01-159312 produces a combustion flame in the vacuum degassing tank, so that a high temperature combustion flame can be obtained. However, the combustion gas is provided on the upper side surface of the degassing tank. Since it is distributed to both the exhaust flue and the dip pipe installed in the lower part, it is necessary to make the incidental equipment installed in the exhaust flue connected to the vacuum system a heat resistant structure or to reduce the passing gas temperature. Become. Also, since the supplied combustion energy is divided into two, heat deposition efficiency is reduced and heating time is extended.Therefore, combustion temperature control and strict combustion gas shunt control are required to match the vacuum degassing schedule. It

The present invention provides a heating method for a vacuum degassing tank, which solves the problems inherent in the above-mentioned prior art and applies a high-temperature combustion flame with good heat-transfer efficiency.

[0008]

DISCLOSURE OF THE INVENTION According to the present invention, a heating burner is inserted from the top of the vacuum degassing tank with only the immersion pipe portion of the vacuum degassing tank open, and an annular high temperature combustion flame of the burner is inserted. Is a method for heating a vacuum degassing tank, characterized in that the amount of radiant energy from the high temperature combustion flame is controlled by adjusting the amount of secondary combustion air supplied to the center of the heating burner. The method for heating the vacuum degassing tank is characterized in that the position is adjusted appropriately.

[0009]

When the vacuum degassing tank is used for the degassing process, the degassing tank and the vacuum system are connected by the exhaust duct.
In the heating of the present invention, the vicinity of the connecting portion of the exhaust duct connected to the vacuum degassing tank is closed with a heat resistant cutoff valve. Therefore, the vacuum degassing tank is in a state in which only the immersion pipe portion is opened.

The heating burner 1 shown in FIG. 1 is inserted from the top of the vacuum degassing tank in the above state. The burner 1 preferably has a structure in which a plurality of pure oxygen burners 2 are annularly arranged and an air supply hole 3 for secondary combustion is provided in the center thereof. An annular high temperature combustion flame is formed by the annular pure oxygen burner 2, and the high temperature combustion flame is a short flame that locally emits high radiant energy. Since the heating burner 1 is exposed to the high temperature atmosphere in the vacuum degassing tank 4 for a relatively long time,
The outer periphery of the heating burner 1 is insulated with a water-cooled jacket structure.

When adjusting the radiant energy distribution of the high temperature combustion flame, air is supplied from the secondary combustion air supply hole 3 provided at the center of the heating burner. By adjusting the supplied air amount, it is possible to obtain a combustion flame having a length corresponding to the supplied air amount. Since the length of the combustion flame is adjusted inside the combustion flame, the distribution of the radiant energy density can be controlled without changing the surface temperature of the combustion flame that contributes to the heating of the inner wall of the vacuum degassing tank.

Therefore, in the case of heat treatment for dissolving and removing a large amount of metal adhered to the local area of the inner wall of the vacuum degassing tank, a high temperature combustion short flame that does not use secondary combustion air is applied at the position of the site height. Then, it can be efficiently dissolved and removed. Also, in the case of heat treatment that dissolves and removes a small amount of metal that adheres to the inner wall of the vacuum degassing tank, by adjusting the supply amount of secondary combustion air to broaden the radiant energy distribution from the high temperature combustion flame,
Although it takes a little longer time, a wide range of metal can be dissolved and removed.

The application of the high temperature combustion flame to the relevant portion of the inner wall of the vacuum degassing tank is achieved by adjusting the insertion depth position of the heating burner. The adhesion position of the metal generated in the vacuum degassing process hardly changes unless the vacuum degassing condition changes, and the adhesion situation shows a similar adhesion pattern. The heating burner can be arranged and executed at a preset insertion depth position corresponding to the melting process.

As another mode of the heat treatment of the inner wall of the vacuum degassing tank, there is a preheat treatment in a standby state before being applied to the vacuum degassing treatment, in addition to the melting and removing treatment of the metal. Since the high temperature combustion flame is often not required in the preheat treatment during the stand-by, unlike the above-described ingot removal treatment, for example, the amount of fuel to be supplied is reduced and the supply amount of secondary combustion air is adjusted. Then, a high-temperature combustion flame having an amount of radiant energy suitable for preheating is generated, and by heating for a set time, it is possible to preheat to a target temperature.

As another mode of the heat treatment of the inner wall of the vacuum degassing tank, there is heating for drying after repairing the lining of the vacuum degassing tank and subsequent preheat treatment. In this case as well, the amount of fuel supplied to the heating burner is reduced and the amount of secondary combustion air supplied is adjusted in the same manner as above to generate a high temperature combustion flame with an amount of radiant energy suitable for the drying process, and heating is performed for a set time By doing so, it can be dried and heated to a target temperature.

[0016]

EXAMPLE As shown in FIG. 2, after completion of the vacuum degassing process,
The heat-resistant shut-off valve 6 shuts off the vicinity of the connection of the exhaust duct 5 of the vacuum degassing tank 4, and the heating burner 1 is inserted from the top 7 of the vacuum degassing tank 4 so as to be vertically movable. Coke oven gas is used as fuel to 800Nm ³ / h and pure oxygen is 1120Nm in order to locally heat the area with a large amount of deposited metal.
³ / h, central secondary fuel air was supplied at 200 Nm ³ / h to make the high temperature combustion flame a relatively short flame, and the metal was melted and removed and heated for 1 hour. Then, a heating burner was applied between zones a and b. Ascend, fuel 600 Nm ³ / h, pure oxygen 840 Nm ³
/ H, the air for secondary combustion was changed to 200 Nm ³ / h, and the high temperature combustion flame was set to a slightly longer flame to perform preheating and heat retention heating.

Almost all of the metal in the vacuum degassing tank where bc was adhered was dissolved and removed, and the inner wall temperature of each region was raised as shown in FIG. As a result of vacuum degassing treatment using this vacuum degassing tank, the temperature drop of the molten steel could be suppressed to 20 ° C.

[0018]

In the case of the conventional heating of about 1000 ° C., the molten steel temperature was lowered by 30 ° C. However, according to the present invention, the adhered metal can be effectively melted and removed, and it is desired by the preheating heating with reduced fuel. The temperature can be maintained at the temperature of, and the non-operation time of the vacuum degassing tank can be reduced by about 20%.

[Brief description of drawings]

FIG. 1 is an explanatory view of a heating burner, in which (a) is a longitudinal sectional view,
(B) is a bottom view.

FIG. 2 is an explanatory diagram of an example of a heating aspect of the present invention.

FIG. 3 is a diagram showing a relationship between temperature and heating time in Examples.

[Explanation of symbols]

1 ... Heating burner 2 ... Annularly arranged pure oxygen burner 3 ... Secondary air supply hole 4 ... Vacuum degassing tank 5 ... Exhaust duct 6 ... Heat-resistant shutoff valve 7 ... Degassing tank top.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Hideki Yamauchi 5-3 Tokai-cho, Tokai-shi Nippon Steel Corporation Nagoya Works (72) Inventor Naoki Yoshida 5-3 Tokai-cho, Tokai-shi Nippon Steel Co., Ltd. Company Inside Nagoya Steel Works

Claims (2)

[Claims] 1. A secondary combustion system in which a heating burner is inserted from the top of the vacuum degassing tank with only the immersion pipe portion of the vacuum degassing tank open, and which is supplied to the center of the annular high temperature combustion flame of the burner. A method for heating a vacuum degassing tank, wherein the amount of radiant energy from the high temperature combustion flame is controlled by adjusting the amount of air for use. 2. The method for heating a vacuum degassing tank according to claim 1, wherein the insertion position of the heating burner is adjusted appropriately.